The present invention relates to a structural member produced by directly adhering a heat resistant fluorine-containing polymer to a substrate, particularly a structural member having enhanced adhesive strength at high temperature, and a structural member produced by providing a layer of fluorine-containing polymer or heat resistant engineering plastic having heat resistance and sliding properties (friction property, abrasion resistance) on the fluorine-containing polymer layer of the above-mentioned structural member.
Further the present invention relates to a multi-layered sliding material and sliding parts having improved heat resistance of adhesive strength and produced by using those structural members.
Fluorine-containing polymers represented by PTFE and PFA and compositions reinforced by blending a filler thereto are used for sliding material and parts because of excellent heat resistance, friction property and abrasion resistance. For example, a steel substrate on which the above-mentioned fluorine-containing material is applied is used as a bearing for general industrial machinery.
However the fluorine-containing polymers have a substantial problem that adhesion thereof to a substrate of metal, etc. is poor due to excellent non-sticking property and friction property thereof.
For adhering a fluorine-containing polymer film or sheet to a metal, there is used, for example, a method of subjecting an adhering surface of the film to chemical preparation treatment such as sodium etching and then adhering the film to the metallic substrate subjected to roughening of a surface thereof physically by sand blasting or the like by using an epoxy resin adhesive.
However that method has problems that
{circle around (1)} there are a danger in handling a sodium etching treating solution and a fear of environmental contamination, and much time and labor are required for processing including treatment of the epoxy resin adhesive, which causes an increase in cost,
{circle around (2)} the fluorine-containing polymer itself is deteriorated by the chemical surface preparation by sodium etching and heat resistance thereof is lowered,
{circle around (3)} heat resistance of an epoxy resin to be used as an adhesive is insufficient and the resin is deteriorated to cause air bubbles and peeling when used at high temperature for a long period of time, and
{circle around (4)} an adhesive strength of the obtained laminated article is insufficient, and even if the adhesive strength is maintained at room temperature, in case of a high temperature, particularly at a temperature of not less than 150xc2x0 C., the adhesive strength is lowered rapidly.
Particularly due to the problems of {circle around (3)} and {circle around (4)}, it is difficult to use those laminated sliding materials for a bearing to be used for internal combustion engine which is subject to high temperature and high load.
Objects of the present invention are to provide a structural member which is produced by directly adhering a fluorine-containing polymer to a substrate and has improved adhesive strength particularly at high temperature, and to provide a sliding material and sliding parts such as a bearing which are excellent in heat resistance of adhesive strength by laminating a material of fluorine-containing polymer or heat resistant engineering plastic excellent in sliding property to the above-mentioned structural member.
The inventors of the present invention have made intensive studies to achieve the above-mentioned purpose, and as a result, have found that when a structural member is produced by directly adhering, to a substrate, a layer of a specific heat resistant fluorine-containing polymer under the condition of the polymer substantially containing no adhesive material other than the fluorine-containing polymer and without using an adhesive layer of a binder or the like, an adhesive strength at high temperature can be improved.
Namely, the structural member of the present invention comprises (A) a layer which comprises a fluorine-containing polymer and does not contain an adhesive material other than the fluorine-containing polymer substantially and (B) a substrate, in which the layer (A) is adhered directly to the substrate (B) without interposing a binder therebetween and a longitudinal shear strength between the layer (A) and the substrate (B) is not less than 0.98 N/mm2 (10 kgf/cm2) at 150xc2x0 C.
The structural member of the present invention can be used effectively for applications exposed to high temperature such as a sliding material, OA roll, OA belt, heating apparatuses for cooking and heat resistant electric wire.